In general, the following two types of exposure apparatus are typical exposure apparatus used in the manufacture of semiconductor devices and the like: a step-and-repeat exposure apparatus (also referred to as a “stepper”) in which, while a substrate (wafer or glass plate) is moved step by step, a plurality of exposure areas on the substrate are successively exposed to a pattern on a master plate (a reticle or mask) via a projection optical system, and a step-and-scan exposure apparatus (also referred to as a scanner) in which exposure transfer of a pattern to a plurality of areas on a substrate is repeated by repeating stepping motion and scanning exposure.
These exposure apparatus are equipped with stage devices (a wafer stage and reticle stage) for positioning a wafer or reticle by moving it at high speed. The general structure of such a stage device is illustrated in the specifications of Japanese Patent Publication No. 63-20014 and 6-6248, by way of example. The basic structure of a stage device of this kind will be described with reference to FIGS. 8A and 8B.
FIG. 8A is a plan view illustrating the basic structure of an ordinary stage device, and FIG. 8B is a sectional view of the same. The stage device shown in FIGS. 8A and 8B includes a moving table 1; an X linear-motor movable element 2 for driving the moving table 1 along the X direction; an X linear-motor stator 3 for driving the moving table 1 along the X direction; a Y linear-motor movable element 4 for driving the moving table 1 along the Y direction; a Y linear-motor stator 5 for driving the moving table 1 along the Y direction; a stage base 6, the upper surface of which serves as a guide surface for the moving table 1; a hydrostatic bearing 7 for levitating the moving table 1 a prescribed amount above the stage base 6; an X movable guide 8 for moving the moving table 1 along the X direction; a Y movable guide 9 for moving the moving table 1 along the Y direction; an X stationary guide 10 for guiding the X movable guide 8; and a Y stationary guide 11 for guiding the Y movable guide 9.
The X movable guide 8 in the above arrangement is moved along the X direction, while being guided directly by the X stationary guide 10, by thrust produced by the X linear motors 2 and 3. With movement of the X movable guide 8, the moving table 1 is moved the same amount along the X direction. Operation along the Y direction is similar. Thus, the moving table 1 is capable of being driven along the X and Y directions. Further, though the structural details of the stationary guide differ in each of the specifications of Japanese Patent Publication No. 63-20014 and 6-6248, both are the same in that a stationary guide is provided as a guide for driving the movable guide.
As mentioned above, the ordinary stage device requires a dual guide structure, namely the movable and stationary guides. In case of an arrangement in which the stationary guides have been removed, the X movable guide will be unstable in the direction perpendicular to the thrust of the X linear motor, i.e., along the Y axis, and in the direction of rotation about the Z axis perpendicular to the plane of the stage base. Even if control is performed based upon thrust allocation of the two X linear motors with regard to the direction of rotation about the Z axis, the position along the Y axis will still be unstable. This means that the X stationary guide cannot be omitted. The same is true with regard to the Y stationary guide.
Thus, as set forth above, the conventional stage device is such that the stationary guides, namely two guide mechanisms, are required. A problem which arises is that these must be adjusted in highly reliable fashion. In addition, the apparatus is large in size and high in cost.